Chlamydia bacteria are obligate intracellular organisms with a phylum-defining biphasic developmental cycle that is intrinsically linked to its ability to cause disease. The progression of the chlamydial developmental cycle is regulated by the temporal expression of genes predominantly controlled by RNA polymerase sigma (σ) factors. Sigma 54 (σ⁵⁴) is one of three sigma factors encoded by Chlamydia for which the role and regulon are unknown. CtcC is part of a two-component signal transduction system that is requisite for σ⁵⁴ transcriptional activation. CtcC activation of σ⁵⁴ requires phosphorylation, which relieves inhibition by the CtcC regulatory domain and enables ATP hydrolysis by the ATPase domain. Prior studies with CtcC homologs in other organisms have shown that expression of the ATPase domain alone can activate σ⁵⁴ transcription. Biochemical analysis of CtcC ATPase domain supported the idea of ATP hydrolysis occurring in the absence of the regulatory domain, as well as the presence of an active-site residue essential for ATPase activity (E242). Using recently developed genetic approaches in Chlamydia to induce expression of the CtcC ATPase domain, a transcriptional profile was determined that is expected to reflect the σ⁵⁴ regulon. Computational evaluation revealed that the majority of the differentially expressed genes were preceded by highly conserved σ⁵⁴ promoter elements. Reporter gene analyses using these putative σ⁵⁴ promoters reinforced the accuracy of the model of the proposed regulon. Investigation of the gene products included in this regulon supports the idea that σ⁵⁴ controls expression of genes that are critical for conversion of Chlamydia from replicative reticulate bodies into infectious elementary bodies.

中文翻译：

---

Sigma 54调控的转录与膜重组和转化为沙眼衣原体感染形式期间的III型分泌效应有关。

衣原体细菌是专一性的细胞内生物，具有定义门的双相发育周期，该周期固有地与其引起疾病的能力有关。衣原体发育周期的进程受主要由RNA聚合酶sigma（σ）因子控制的基因的时间表达所调节。西格玛54（σ ⁵⁴）是由编码三个西格玛因素之一衣原体的量，作用和调节子是未知的。CTCC是双组分信号转导系统，该系统必要条件σ的一部分⁵⁴转录激活。CTCC激活σ的⁵⁴需要磷酸化，这减轻了CtcC调节域的抑制作用，并使ATPase结构域能够进行ATP水解。与其他生物的同源物CTCC之前的研究已经表明，ATPase结构域的表达可以单独激活σ ⁵⁴转录。CtcC ATPase结构域的生化分析支持在不存在调节结构域以及存在ATPase活性必不可少的活性位点残基的情况下进行ATP水解的想法（E242）。在使用最近开发的遗传方法衣原体诱导CTCC ATPase结构域的表达，转录谱确定了预期反映σ ⁵⁴regulon。计算评估表明，大多数差异表达的基因的由高度保守的σ前面⁵⁴的启动子元件。使用这些假定的σ报告基因分析^54个促销员增强建议的调节子模型的准确性。包括在这个调节子的基因产物的研究支持了σ ⁵⁴是用于转化的关键基因的表达控制衣原体从复制网状体为感染原体。